Assume that in a completed well it is necessary to use some kind of milling tool for removal of a packer, bridge plug, or the like from the well. This is done by grinding by means of a cutting tool which is affixed on a pipe string. In grinding, shaving are created, and they will ordinarily create a nest around the cutting tool, plugging the well and thereby preventing continued fluid flow. They will clogged the annular space in the well on the exterior of the pipe string supporting the cutter.
The present apparatus is directed to a reverse circulation sub attached to pipe string and which is equipped with a crossover so that circulation can be diverted to the exterior to wash cuttings downwardly and is also provided with an upward flow path through the tool for the circulation which will carry cuttings upwardly into the tool. In the tool itself, the circulation is directed upwardly and into an internally located basket. This basket is defined by a standpipe in the center and a long annular cavity for receiving, storing, and holding cuttings, and is also able to deliver fluid out of this chamber flowing upwardly through a shield which keeps the cuttings in the chamber. This permits the circulating fluid to escape the chamber and complete the circulation flow path.
The present apparatus particularly will hold and capture cuttings, whether long or short, and they are captured at a location where they do not interfere with cutting. The cutter normally is required to operate over a fairly long time interval depending on the size of the object being milled. As it is cut, the shavings are broken and delivered into an internal storage chamber. This storage chamber has sufficient length that circulation into the storage chamber collects most of the cuttings in that chamber. Thus, the tool is run into the well with the chamber empty and is operated for as long as needed, and is also operated to gather and collect all these cuttings in the internal chamber.
The present apparatus is summarized as a reverse circulation crossover sub which receives well fluid through a pipe string where the fluid flows axially through the top part of the tool and is then circulated to the exterior by jets directed to the exterior of the sub. The fluid then flows on the exterior downwardly along the tool to the bottom and around the cutter which is attached at the bottom of the tool. There is a fluid pathway up through the center of the tool, and this pathway is directed upwardly through a bottom sub and then to a standpipe inside a chamber. This chamber is defined by the surrounding sidewall of the tool structure. This chamber collects trash including short chips and long spiral cuttings also. The standpipe is perforated at several midpoints to create a circular flow path carrying the cuttings to the bottom of this chamber. Fluid fills the chamber and flows out the top end through a deflector shield at the top of the chamber. Fluid then flows upwardly from the deflector shield along a pathway on the interior of the tool and then is ultimately routed to the exterior through return ports. This fluid is routed at the very top end of the tool to flow in the annular space. Below these ports, there is a resilient casing pack off which assists in isolating the cutter so that all fluid at the cutter is flowing downwardly on the exterior.